transport layer

Question 1

node to node
host to host
process to process

Answer 1

link layer
network layer
transport layer

Question 2

logical communication between hosts

Answer 2

network layer

Question 3

logical communication between processes

Answer 3

transport layer

Question 4

Transport Layer Functionalities

Answer 4

hiding transmission details
Segmentation and reassembly
Addressing
Multiplexing / Demultiplexing
Reliable data transfer

Question 5

A segment at the transport layer must carry

Answer 5

The destination port to specify remote process
As well as the source port to specify the sender process

Question 6

A UDP socket is fully identified by

Answer 6

a destination IP address and a destination port number.

Question 7

header size:

Answer 7

TCP is 20 bytes, UDP only 8 bytes.

Question 8

sender will not overwhelm receiver

Answer 8

flow controlled:

Question 9

Reactive

Answer 9

resend lost or corrupted packet (error control)

Question 10

Proactive

Answer 10

Prevent packet loss at the receiver buffer (flow control) and at the router buffers (congestion control)

Question 11

ARQ

Answer 11

mechanism that is based on retransmission when detecting an error is called ARQ: Automatic Repeat reQuest

Question 12

TCP Flow Control: How It Works?

Answer 12

The TCP provides flow control by
having the sender maintain a
variable called the receive window.
* The receive window is used to give
the sender an idea of how much free
buffer space is available at the
receiver.
* Host B tells Host A how much spare
room it has in the connection buffer
by placing its current value of rwnd in
the receive window field of every
segment it sends to A.
* Initially, Host B sets rwnd = RcvBuffer.

Question 13

Consequences of Congestion Control

Answer 13

Lost packets (buffer overflow at routers)
Long delays (queuing in router buffers)

Question 14

actual window size

Answer 14

min(cwnd,rwnd)